1. Field of the Invention
This invention relates to water disinfecting systems and particularly those for medical use such as in the field of dentistry.
2. Related Art
Modern dental units contain water supply systems that provide coolant and rinse water to a number of dental instruments, such as for example, high-speed dental hand-pieces, ultrasonic scalers and air and water syringes. Dental professionals have become aware that the microbiologic quality of water used in dental treatment should be improved.
Dental unit waterlines have been shown to harbor a wide variety of microorganisms including bacteria, fungi and protozoa. These microorganisms colonize and replicate on the interior surfaces of the waterline tubing, resulting in microbial accumulations termed "biofilms." Biofilms serve as a reservoir significantly amplifying the numbers of free-floating microorganisms in the water that exits the waterline into the patient's mouth.
Levels of contamination in dental unit treatment water frequently exceed 100,000 colony forming units per milliliter (cfu/ml). Although there is no solid evidence of a public health problem, the presence in dental waterlines of potential human pathogens including Pseudomonas, Legionella, and non-tuberculous Myco-bacterium species suggest reason for concern. The American Dental Association's Council on Scientific Affairs recommended in September, 1995, that by the year 2000, water delivered to patients during non-surgical dental procedures consistently contain no more than 200 colony forming units per milliliter (cfu/ml) of aerobic mesophilic heterotrophic bacteria at any point in time in the unfiltered output of the dental unit.
It is a common practice to slightly heat dental unit water to increase patient comfort because cool water in the patient's mouth can be painful depending on the procedure being performed. However, it has been suggested that the heating of the water for patient comfort may further promote the formation of biofilm.
The conventional methods for addressing the problem of microbial infestation of dental water supply systems are independent water reservoirs, chemical treatment regimens, point of use filters, or oxidation and ozonation. Some of these conventional methods require daily draining and purging regimens even in the case of independent purified water reservoirs. These prior methods are also very costly and some of the chemical treatment regimens have been suspected as causing potentially toxic or carcinogenic byproducts when the treating chemical reacts with the material of the waterline. Also, the chemicals chosen must be bio-compatible because of the possibility that a chemical residue may remain in the waterline. Many of the chemicals proposed for treatment of dental waterlines have the potential to react with the material of the dental water delivery system. For example, chlorine compounds may react with the biofilm or other dissolved organic compounds to produce an undesirable class of chemicals known as tri-halomethanes. Other agents such as bromine and ozone may also produce undesired chemical by-products. Finally, the point of use filtration systems (filter in the hand-piece) does nothing for build-up of biofilms in the waterline and usually the filter has the annoying need to be replaced daily. With the problem of undesired chemical by-products being produced and the problem of high cost and maintenance, this is a difficult problem to solve particularly if one utilizes the prior conventional methods.
One prior art system is shown in U.S. Pat. No. 5,556,279 issued Sep. 17, 1996 to Wolf, which discloses a system which utilizes a combination activated charcoal resin filter and an iodinated fixed rate exchange resin filter which could be categorized as a point-of-use filter system or a point-of-use chemical treatment system. U.S. Pat. No. 5,158,454 issued Oct. 27, 1992 to Viebahn and assigned to Dr. Hanslet, shows ozone radical converters to ozonize water to make the water virtually microbe free. U.S. Pat. No. 4,978,297 issued Dec. 18, 1990 to Vlock, shows an auxiliary chamber to communicate with the water line. The auxiliary chamber can receive an automatically dissolving tablet for disinfectant. U.S. Pat. No. 4,973,247 issued Nov. 27, 1990 to Varnes, shows the removal of the dental unit from the domestic water supply by utilizing a sterile coolant supply. The above noted Wolf U.S. Pat. No. (5,556,279) shows a two stage filter/chemical treatment cartridge and the first stage filters or neutralizes any chlorine from the source water with a charcoal resin and the second stage releases an iodinated resin which neutralizes and kills bacteria. The Viebahn prior art U.S. Pat. No. (5,158,454) uses a type of oxidation to ozonize the water to kill the bacteria. The Vlock U.S. Pat. No. (4,978,297) shows provisions to place a dissolving tablet in the waterline for purification purposes. The Varnes prior art patent U.S. Pat. No. (4,973,247) has a stand alone separate sterilized coolant supply. These patents show that there is a long felt need for sanitary dental water and that the problem continues to be addressed without satisfactory resolution.
As noted in the above discussion of the related art, the methods used in the above cited patents have problems that vary from the possible production of harmful chemical byproducts, to high level cost and maintenance. Better systems are needed, as suggested by the American Dental Association's Council of Scientific Affairs.